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000
FXUS63 KFSD 291929
AFDFSD

AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
229 PM CDT Mon May 29 2023

.SHORT TERM...(This Evening through Tuesday)
Issued at 227 PM CDT Mon May 29 2023

KEY MESSAGES

1. Isolated to scattered thunderstorms this evening and overnight
with a lower end threat of strong storms.

2. Almost daily shower and thunderstorm chances continue through the
week with far more dry periods than wet.

3. Above normal temperatures continue with highs in the 80s to near
90.


Rest of Afternoon/Evening: Memorial Day featuring weather typical of
the unofficial start to summer this year with sunshine and
temperatures in the 80s this afternoon giving way to scattered
thunderstorm chances later. Mesoanalysis suggest only a weak to non-
existent cap in place but not much of focus to more substantial
lift to cause anything more than a Cu field at this time other
than weaker convection exiting into MN. Forecast soundings and
short range guidance suggest this weak cap erodes further and thus
at least slight chance POPs become justified most locations by
late afternoon/early evening. With this said, a couple of
different waves may provide for a bit better focus of convection
chances deeper into the evening hours.

Main mid level wave is currently evident on WV imagery lifting into
the western Dakotas with a secondary weaker wave progged to slide
east through Nebraska this evening. This may set up two foci for
better thunderstorm coverage, one near and north of Hwy 14 and
another near and south of the MO River. This idea is further
supported by several CAMS and HREF thunder probabilities.

In terms of severe weather chances... deep layer shear remains weak
with EBWD values of only 20-25 kts in most locations. MLCAPE does
sit in the 1500-2000 J/kg, locally higher, so initial updrafts would
carry the risk for up to half dollar to ping pong ball size hail
before likely collapsing on themselves. Forecast soundings
encroaching on inverted-V and DCAPE values in excess of 1000 J/kg
also result in a risk for wind gusts up to 60-70 mph, but again,
with a lack of shear, organization will be tough to come by. These
threats are highlighted by a Marginal Risk from SPC for points near
and west of I-29 and a Slight across south central SD.

Tonight: Any thunderstorm activity will continue to work east
overnight but will likely see a diminishing severe weather threat as
instability wanes and LLJ support decreases. Overnight lows in the
mid 50s to mid 60s are expected.

Tuesday: No real change in the overall pattern for Tuesday with
thermal profiles again favoring high temperatures in the 80s,
perhaps making a run at 90 in some locations. Atmosphere largely
only weakly capped, if at all, by late afternoon again but no real
trigger for convection. Will keep low end POPs for any rogue storm
chance.

The better chance of convection likely arrives into the late evening
and overnight hours as another wave lifts northeast out of Nebraska
and should result in expanding thunderstorms. Similar threats to
today`s in terms of severe weather but overall remains on the low
side.

.LONG TERM...(Tuesday Night through Monday)
Issued at 227 PM CDT Mon May 29 2023

Wednesday through Sunday: The upper level flow pattern remains weak
into the weekend with upper level ridging trying to back westward
into the region. This may ultimately keep any late week shower and
thunderstorm chances more on the isolated to scattered side but with
weak waves in the flow and an atmosphere only weakly capped, likely
one with daily rain chances. Timing of any thunderstorm chances will
be much more nebulous with likely at least some favor to the late
afternoon and evening diurnal periods. High temperatures again
remain fairly steady state, or 80s to near 90s and lows in the
60s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday Afternoon)
Issued at 1141 AM CDT Mon May 29 2023

Weak morning convection has largely moved east of the area and/or
decayed. Forecast soundings show enough moisture around 5-7 kft to
allow for some Cu this afternoon but VFR conditions expected to
prevail. By later afternoon, and probably more likely
evening/early overnight, should see the chance for scattered
showers and thunderstorm increase. Timing or impact level an any
individual terminal still a bit nebulous but tried to time in
rough highest probability timing.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&

$$

SHORT TERM...Kalin
LONG TERM...Kalin
AVIATION...Kalin